Rocker and Ajax native Deryck Whibley and his girlfriend dressed up as his ex-wife Avril Lavigne and her fiancé Chad Kroeger (Kroeger <a href="http://www.calgaryherald.com/Chad+Kroeger+slams+Deryck+Whibley+over+Chavril+costume/7469186/story.html">wasn’t too keen on the costume</a>)